Writing Unit Tests with JUnit - touniez/comp402doc GitHub Wiki

With the JUnit framework, unit tests are any public classes that extend the junit.framework.TestCase class, and that have any number of methods with names beginning with the word "test". JUnit provides methods to easily assert things about your own classes, as well as the ability to run a group of tests.

The requirements for writing unit test classes are described below, with an example provided in the next section. In general, though, the intent is for you to create instances of your classes in the test methods, get results from any methods that you call, and assert that those results match your expectations. If these assertions pass, then your program has behaved correctly and your tests have succeeded.

To use DrJava's Test command on a document, you must use the programming conventions outlined below. You can also choose the "New JUnit Test Case" command from the File menu to automatically generate a template with these conventions.

• At the top of the file, include:

  import
                            junit.framework.TestCase;
  

• The main class of the file must:

  • be public

  • extend TestCase

• Methods of this class to be run automatically when the Test command is invoked must:

  • be public and not static

  • return void

  • take no arguments

  • have a name beginning with "test"

• Test methods in this class can call any of the following methods (among others):

  • void assertTrue(String, boolean)

    which issues an error report with the given string if the boolean is false.

  • void assertEquals(String, int, int)

    which issues an error report with the given string if the two integers are not equal. The first int is the expected value, and the second int is the actual (tested) value. Note that this method can also be called using any primitives or with Objects, using their equals() methods for comparison.

  • void fail(String)

    which immediately causes the test to fail, issuing an error report with the given string.

  Test methods are permitted to throw any type of exception, as long as it is declared in the "throws" clause of the method contract. If an exception is thrown, the test fails immediately.

• If there is any common setup work to be done before running each test (such as initializing instance variables), do it in the body of a method with the following contract:

  protected void setUp()
  

  This method is automatically run before any tests in the class. (Similarly, you can write a protected void tearDown() method to be called after each test.)

• If you would rather control which methods are called when running the tests (rather than using all methods starting with "test"), you can write a method to create a test suite. This method should be of the form:

             public static Test suite() { TestSuite suite = new TestSuite();
             suite.addTest(new <classname>("<methodname>")); ...
             return suite; } 
  

  It is then also necessary to import TestSuite and Test from junit.framework. There is also a version of the addTest method that takes a Test, so test suites can be composed.

A simple example of a TestCase class is given in the next section. There are many other ways to use JUnit, as well. See the JUnit Cookbook at http://junit.sourceforge.net/doc/cookbook/cookbook.htm for more examples and information.